Need help, Mumble server

Ok so a few months ago I created a mumble server with the raspberry pi as an alternative to Skype and its general system hording ways. I've got limited real world knowledge on networking and the works. However I would really like to segment my network so I could have my family on one, gaming rigs on one, and my mumble and possibly Minecraft server on another. I have looked into subnets and vlans and have come up dry. Do I buy new routers and follow some tutorials online on how to make a "lab network", or do I just not really worry about it. There are, as I suspect in most households on this forum, pcs' who have mission crucial data. i.e pictures, school work, that I wouldn't want to risk because of some mumble server not being configured on my network correctly. I understand port forwarding in any since posses a degree of danger but I want to this as safe as possible. I suppose what I need to know is where do I go from here? What do I research? What do need?

To be honest, you shouldn't have a problem as long as you are only port forwarding the required ports for VOIP to the mumble server (and not say port 22).

Consumer routers are a bit lacking when it comes to actual networking features... which is kind of bad. If you have a spare router you could double firewall if you are really worried.
In short you would place the server between the two firewalls.

Modem -> Router -> Server Space -> Router -> All the other mission critical stuff.

Essentially doing this will stop anything that can enter the server space entering the other critical stuff due to the double firewall. (This does require some playing of subnets to stop the inner conflicting with the not so inner network.

Alternatively you could get something like an old Watchguard X550e and flash it with PfSense and do the above setup with just one router.